1. Field
The field of the invention is workworking lathe components, and more particularly such components employed for boring deep holes in elongate workpieces.
2. State of the Art
Boring large length-to-diameter holes lengthwise into slender wooden workpieces with a high degree of straightness and directional control has long been regarded as very difficult. Generally, such long small holes are employed in dimensionally uncritical bulky objects, where crookedness and erratic direction is not objectionable. For lathe turned products, the workpiece is commonly gripped cantilevered from its head end from a chuck mounted in the lathe headstock.
An appropriately sized drill bit is installed, also cantilevered, in a chuck mounted on a sliding shaft carried by the lathe tailstock. The shaft is urged toward the headstock, pressing the cutting end of the bit into the projecting end of the workpiece. Since both the workpiece and the drill bit are only gripped at one end, both are subject to deflection during the drilling operation. The locations of the drill bit and the workpiece could be exchanged, with the latter being urged against the former as it rotates. However, the same shortcomings exist. These methods work well for spool spindle holes, wheel axle bores, and other short bores, but are unsatisfactory for long slender bores, requiring long slender drill bits, especially when the workpieces are similarly proportioned, as often is the case. Limberness of both workpiece spindles and bits, always aggravated by deflection of the latter by variations in wood grain direction and hardness, combine to generally prevent the drilling of reasonably straight, accurately directed, small deep bores. Examples include the small diameter deep holes required in turned writing pen barrels, upstanding lamp posts and the like.